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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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246                                ALASKAN GLACIER STUDIES
tributary cascading out of a lofty hanging valley, ends in a moraine-covered nose, beneath which a stream emerges from an ice cave. About two miles from the edge of Valdez Glacier the clear ice begins, and thence eastward to the summit the surface is bare of moraine. There are no medial moraines but there are broad lateral moraines, that on the south side being widest, partly because of the supply from the cascading tributary.
Surface of Valdez Glacier. The surface of Valdez Glacier is generally clear and free from moraine except along the margins and near the terminus. It is moderately cre-vassed (PI. XCIV, B), but melting has rounded the seracs and reduced their height so that the crevasses are rather broad, and none of them deep. One can make fairly easy and rapid progress over the glacier surface by winding back and forth between crevasses. The surface is made up of coarsely-crystalline ice so melted along the crystal faces for the upper six inches that it is granular and crumbles as one walks over it. Pieces one or two inches square can be picked out and through each numerous holes and cracks extend.
The lateral moraines are a mere veneer of slabby, angular debris upon the surface. In the east lateral moraine, where the ice is somewhat crevassed, the veneer is so thin that sheer cliffs stand out as a result of melting, and the crevasses are only partly filled. Upon the lateral moraines and the debris-laden terminus are numerous lines of flat stones whose linear arrangement suggests that they represent the bottom of former crevasses. Some of the lines of these crevasse deposits now stand in relief. There are also numerous cones near the terminus of the glacier that appear to be piles of dirt but are really cones of ice (PI. XCVII, A), very thinly veneered with fine black slate fragments, which have protected the ice and kept it from melting. Some of these are six or eight feet high, and some are low and in form resemble ant hills. Many of these smaller cones are also in lines and suggest moulin deposits along the bottom of crevasses. There are occasional glacier tables where flat rocks stand upon a column of ice which has been protected from melting. The material upon the glacier surface is predominantly slate and graywacke of the Valdez series with a few crystalline rocks, such as might come from the granitic diorite dikes of the area drained by the glacier and its tributaries.
Front of Kaldez Glacier. The terminus of the glacier slopes gently (PI. XCVIII, A) and is continuously dirty. Near the eastern side two rock knobs, each over a hundred feet high, rise at the edge of the glacier, being the only rock hills exposed away from the valley walls. East of these the largest stream emerges and the lateral moraine is wide, while to the west a V-shaped area of debris-covered ice extends far up the glacier. The west lateral moraine is also broad but is interrupted by the area of crevassing where the glacier turns snarply at the bend in the valley less than a mile from the end. The debris-covered portion of the terminus is narrowest in the middle of the glacier between the west lateral moraine and the medial moraine.
The streams emerging from the middle of the glacier front in 1909 were of small size and there were no good-sized frontal lakes, though there were several small ones. The stream on the west side was much smaller than that on the east. The drainage evidently shifts back and forth across the ice front, as is shown by the abandoned stream channels and terraces and the absence of vegetation upon the outwash gravels in front of the glacier. The largest stream has, however, remained on the east side of the glacier since 1898; there has sometimes been a stream in the center and sometimes not; and the stream on